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NONDESTRUCTIVE TESTS TO DETERMINE CONCRETE STRENGTH - A STATUS REPORT

Individual and combined nondestructive test methods have been critically reviewed as potential methods to determine safe formwork removal times. The techniques reviewed are the Windsor probe, the Schmidt Rebound Hammer, pull-out measurements, push-out cylinders, ultrasonic pulse velocity measurements, and the maturity and equivalent age concepts. The individual methods, themselves, do not give good estimates of the in situ strengths of concretes and it is recommended that future research emphasize combined methods. A proposed research program which emphasizes combined nondestructive test methods has been developed.